Equal Channel Angular Rolling Research Articles

RETRACTED: Shi et al. Effect of Final Rolling Temperature on Microstructures and Mechanical Properties of AZ31 Alloy Sheets Prepared by Equal Channel Angular Rolling and Continuous Bending. Materials 2020, 13, 3346

The journal retracts the article, “Effect of Final Rolling Temperature on Microstructures and Mechanical Properties of AZ31 Alloy Sheets Prepared by Equal Channel Angular Rolling and Continuous Bending” [...]

Strength and formability improvement of ECARed aluminum alloy 6061 sheets using the artificial aging heat treatment

In the current research, the experimental investigation of the mechanical characteristics of 6061 aluminum alloy, which was subjected to Equal Channel Angular Rolling (ECAR) – A Severe Plastic Deformation Process – and artificial aging heat treatment, has been discussed. By performing the ECAR, the strength of the material increases, but the formability will be reduced. Consequently, the usage of this alloy has been limited. The artificial aging heat treatment process has been proposed after the ECAR operation, and the strength, hardness, and formability of the material have been investigated. In this regard, remarkable results were obtained. By controlling the aging time and temperature on the ECAR piece, not only the strength increased but also the ductility increased. Moreover, an artificial neural network was used to find the optimal aging time and temperature. Finally, the best aging time and temperature ranges to achieve the most desirable mechanical properties were provided using the neural network. The result show 150% increase in strength and 50% in formability by performing controlled-artificial aging heat treatment with ECAR process.

Microstructure evolution and twinning behavior of AZ31 magnesium alloy sheets with bimodal texture during cold deep-drawing deformation

Cold deep drawing experiments were conducted on AZ31 magnesium (Mg) alloy sheets with bimodal texture, which were prepared by the newly developed equal channel angular rolling and continuous bending and subsequent annealing (ECAR-CB-A) process. The results showed that the sheet could be successfully deep-drawn at a limiting drawing ratio (LDR) of 1.6, and the forming performance was better than that of the as-rolled base-texture sheet at room temperature. The microstructure after deep-drawing deformation was investigated by X-ray diffraction (XRD), optical microstructure (OM), and electron backscatter diffraction (EBSD). A large number of {10−12} extension twins (ETs) are observed in the outer shoulder region. Due to the bimodal texture, the activated {10−12} ET variants and the basal slip within the matrix have a higher Schmid Factor (SF) value when the outer shoulder region is under radial tensile stress, this enables the shoulder of the drawn cup to maintain good deformability. In addition, some {10−11} contraction twins (CTs) and {10−11}-{10−12} double twins (DTs) can be observed in this region, which is activated by the local strain accommodation between the twins and the slip systems, and the multiaxial stress. Due to different stress conditions, the volume fractions of {10−12} ETs in the inner shoulder region are less than that in the outer region. The stress concentration caused by {10−11}-{10−12} DTs that occurred in the edge region is the reason for the fracture of the drawn cups at a drawing ratio(DR) of 1.7.

Role of unusual double-peak texture in significantly enhancing cold rolling formability of AZ31 magnesium alloy sheet

Multi-pass cold rolling experiments were performed on AZ31 magnesium alloy sheet with unusual double-peak texture, where basal poles tilt about ±40° away from normal direction to rolling direction. This adopted sheet was fabricated by a novel technology of equal channel angular rolling and continuous bending process with subsequent annealing. Experimental results confirm that such an unusual double-peak texture contributes to a huge improvement of accumulated reduction up to 39.2%, which is over twice as much as that (18.3%) in sheet with strong basal texture. Optical microscopy and electron backscatter diffraction measurements demonstrate that the evolution of microstructure and texture in sheet with unusual double-peak texture is quite different from that in sheet with strong basal texture. Schmid factor (SF) analysis confirms that sheet with unusual double-peak texture possesses obviously large SF values for basal 〈a〉 slip {1012} and extension twin (ET) and remarkably small SF values for prismatic 〈a〉 slip and pyramidal 〈c+a〉 slip during cold rolling process. Therefore, basal 〈a〉 {1012} slip and {1012} ET will be activated more frequently in sheet with unusual double-peak texture to sustain plastic strain, leading to significant enhancement in cold rolling formability.

Effects of equal channel angular rolling process on the mechanical properties of Al-Cu two-layer sheets: experimental and numerical approaches

Abstract This study investigates the mechanical properties and microstructural characteristics of explosion-welded Al/Cu two-layer strips during the ECAR process using finite element simulations and experiments. Furthermore, the explosion-welded Al/Cu two-layer strip was examined with various configurations to determine the effects of die angle and friction coefficient on the distributions of effective strain and stress. In addition, the experimental and computational approaches were utilized to explore the ECAR process in two routes, RA and RC, for three directions. Finite element simulations were run and validated using experimental data. The findings show that the ECAR method is effective to enhance the mechanical characteristics of the strips. Moreover, the obtained results represent that the ECAR process reduced the size of the grains. Furthermore, it was shown that by increasing the number of routes in the ECAR process, the stress values were increased. However, the ductility of the two-layer strip was decreased. According to the current study, the route and the number of routes used in the ECAR process have a considerable effect on the strength of the two-layer strip.

RT ECAP and rolling bestow high strength and good ductility on a low lithium aluminum alloy

The pivotal role of lithium (Li) in improving the comprehensive mechanical properties of third-generation Al–Li alloys remains significant even at a low content. However, the strengthening contribution of a low dosage lithium and its combination with different processing methods remain largely unknown. This study aimed to investigate the strengthening effects of room-temperature (RT) equal channel angular pressing (ECAP) and rolling on Al–0.6Li alloy. Microstructural evolution during processing was monitored by optical microscope (OM), scanning electron microscope (SEM), electron backscattered diffraction (EBSD), transmission electron microscope (TEM) and X-ray diffraction (XRD). The results revealed that simultaneous high ultimate tensile strength (UTS, 243 MPa) and yield strength (YS, 210 MPa) of the developed Al–0.6Li alloy were specifically achieved with a combination of RT ECAP and rolling, alongside an elongation (EL) of 9.5%. The gained strength improvement was primarily credited to the excellent fine-grain strengthening, as evidenced by a significant reduction in grain size from 101 μm to 1.47 μm, and dislocation strengthening, which, respectively, contributed to an increase of 91 MPa and 100 MPa in YS. Findings from this study demonstrate that with proper processing technology, the mechanical properties of Al–Li alloys with low Li content can be effectively improved, opening new avenues to develop high-performance Al–Li alloys.

Evaluation of Powder Metallurgy Workpiece Prepared by Equal Channel Angular Rolling.

The aim of the article is to examine the workability of sintered powder material of aluminum alloy (Alumix 321) through severe plastic deformations under the conditions of the equal channel angular rolling (ECAR) process. Accordingly, the stress-strain analysis of the ECAR was carried out through a computer simulation using the finite element method (FEM) by Deform 3D software. Additionally, the formability of the ALUMIX 321 was investigated using the diametrical compression (DC) test, which was measured and analyzed by digital image correlation and finite element simulation. The relationship between failure mode and stress state in the ECAR process and the DC test was quantified using stress triaxiality and Lode angle parameter. It is concluded that the sintered powder material during the ECAR processing failure by a shearing fracture because in the fracture location the stress conditions were close to the pure shear (η and θ¯ ≈ 0). Moreover, the DC test revealed the potential role as the method of calibration of the fracture locus for stress conditions between the pure shear and the axial symmetry compression.

Finite Element Analysis and Optimization of Equal-Channel Angular Rolling Process by Using Taguchi Methodology

Finite Element Analysis and Optimization of Equal-Channel Angular Rolling Process by Using Taguchi Methodology

Influence of bimodal non-basal texture on microstructure characteristics, texture evolution and deformation mechanisms of AZ31 magnesium alloy sheet rolled at liquid-nitrogen temperature

Cryogenic rolling experiments have been conducted on the AZ31 magnesium (Mg) alloy sheet with bimodal non-basal texture, which is fabricated via the newly developed equal channel angular rolling and continuous bending process with subsequent annealing (ECAR-CB-A) process. Results demonstrate that this sheet shows no edge cracks until the accumulated thickness reduction reaches about 18.5%, which is about 105.6% larger than that of the sheet with traditional basal texture. Characterization experiments including optical microstructure (OM), X-ray diffractometer (XRD), and electron backscatter diffraction (EBSD) measurements are then performed to explore the microstructure characteristics, texture evolution and deformation mechanisms during cryogenic rolling. Experimental observations confirm the occurrence of abundant {10–12} extension twins (ETs), twin-twin interactions among {10–12} ET variants and {10–12}-{10–12} double twins (DTs). The twinning behaviors as for {10–12} ETs are responsible for the concentration of c-axes of grains towards normal direction (ND) and the formation of transverse direction (TD)-component texture at the beginning of cryogenic rolling. The twinning behaviors with respect to {10–12}-{10–12} DTs are responsible for the disappearance of TD-component texture at the later stage of cryogenic rolling. The involved deformation mechanisms can be summarized as follows: Firstly {10–12} ETs dominate the plastic deformation. Subsequently, dislocation slip, especially basal <a> slip, starts to sustain more plastic strain, while {10–12} ETs occur more frequently and enlarge continuously, resulting in the formation of twin-twin interaction among {10–12} ET variants. With the increasing rolling passes, {10–12}-{10–12} DTs incorporate in the plastic deformation and dislocation slip serves as the major one to sustain plastic strain. The activities of basal <a> slip, {10–12} ETs and {10–12}-{10–12} DTs benefit in accommodating the plastic strain in sheet thickness, which contributes to the improved rolling formability in AZ31 Mg alloy sheet with bimodal non-basal texture during cryogenic rolling.

Dislocation structure and crystallite size distribution in plastically deformed Ti determined by X-ray peak profile analysis

Abstract Ultrafine-grained titanium produced by equal channel angular pressing and subsequent cold rolling is studied by X-ray diffraction. It is found that a texture exists in which the hexagonal basal planes are parallel to the longitudinal axis of the billet. The crystallite size distribution and the dislocation structure are determined by X-ray diffraction peak profile analysis. The median and the variance of the crystallite size distribution are obtained as m = 39 nm and σ = 0.14, respectively. The dislocation model of anisotropic broadening of peak profiles enables to determine the active slip systems. It was found that all three possible hexagonal Burgers vectors of dislocations exist, with the composition of 66% &lt;a&gt; type, 33% &lt;c&gt; type and 1% &lt;c + a&gt; type.

Mehaničke karakteristike legura AL-1050 i AL-6061 deformisanih korišćenjem ravnokanalnog procesa ugaonog valjanja

One of the effective severe plastic deformations (SPD) techniques is Equal channel angular rolling (ECAR) process which can lead to proper ultra-fine grained (UFG) structures of material, the main objective of this work is to study the improvement in mechanical properties within 1050 and 6061 aluminum alloy sheets. There are more attempts to investigate the microstructure and mechanical properties of strips material, the influence of process parameters such as number of equal channel angular rolling passes, routes (A&amp;C) and annealing temperature after each passes on deformation behavior of 6061 and 1050 Aluminum alloys were investigated experimentally .Results was indicated that for AL-6061 without annealing process at first pass it was the higher stress than the passes after annealing process and also the grains was fine in the first pass ,For AL-1050 it was indicated that with ambient temperature at six pass the mechanical properties was improved and its recorded the higher stress with more passes at six pass for rout C and also the fine grains of microstructure was obtained in the six pass with compared to the material with annealing process which becomes more ductility with more passes.

Microstructure and mechanical properties of SiCp/AZ91 composites processed by a combined processing method of equal channel angular pressing and rolling

In this study, SiCp/AZ91 composites with enhanced mechanical properties was successfully obtained by a combined process route of equal channel angular pressing (ECAP) and rolling. The effect of ECAP and rolling on the microstructure and mechanical properties of SiCp/AZ91 composites were investigated by comparative analysis. Results showed that the high-pass ECAP process effectively refined the matrix grains and dispersed the SiCp, which gave rise to the final formation of homogenous microstructure in the rolled plate. A non-basal texture with high Schmidt factors was formed by ECAP process, while after rolling it turned into basal texture with relatively lower Schmidt factors. The SiCp/AZ91 composite obtained by the combined process method exhibited superior mechanical properties (yield strength of ∼348 MPa, ultimate strength of ∼411 MPa) and improved ductility (elongation of ∼6.3%) than the composite singly processed by rolling. The enhanced mechanical properties should be contributed to the homogenized microstructure with refined grains, uniformly distributed SiCp, accumulated dislocations and transferred texture.

Investigation of the Correlation between Initial Microstructure and Critical Current Density of Nb-46.5 wt%Ti Superconducting Material

We have investigated the effect of initial microstructures on the change in critical current density (Jc) of Nb-46.5 wt%Ti (NbTi) superconducting material. It is well known that α-Ti phases distributed in NbTi material act as a flux pinning center, resulting in an improvement in critical current density. Therefore, it is crucial to obtain the grain-refined microstructure, which is strongly related with precipitation of uniformly distributed fine α-Ti phases and higher volume faction of α-Ti phases, as α-Ti phases are precipitated at the grain boundaries and triple points during heat treatments. Therefore, in order to characterize the effect of initial microstructure of NbTi on critical current density, different initial microstructures were obtained by applying equal channel angular pressing (ECAP) and hot rolling with different strains. It was revealed experimentally that hot rolling with a higher strain is efficient for obtaining the initial microstructure, which has equiaxed fine grains of β-NbTi with the aid of dynamic recrystallization, and which is helpful for precipitating fine α-Ti phases during intermediate heat treatment. Furthermore, it was confirmed that critical current density can be enhanced by obtaining a smaller α-Ti phase, a higher aspect ratio of α-Ti phase, a higher volume fraction of α-Ti phase and a ribbon-like folded α-Ti phase.

Tailoring Extra-Strength of a TWIP Steel by Combination of Multi-Pass Equal-Channel Angular Pressing and Warm Rolling

Increasing the yield stress of twinning-induced plasticity (TWIP) steels is a demanding task for modern materials science. This aim can be achieved by microstructure refinement induced by heavy straining. We feature the microstructural evolution and mechanical performance of a high-manganese TWIP steel subjected to deformation treatment by different combinations of equal channel angular pressing (ECAP) and rolling at different temperatures. The effect of microstructure on the tensile properties of the steel subjected to the multi-pass ECAP process and to subsequent rolling is reported as well. We show that the combined deformation procedure allows us to further increase the strength of the processed workpieces due to a gradual transition from a banded structure to a heterogeneous hierarchical microstructure consisting of fragments, dislocation configurations and nano- and micro-twins colonies. Rolling of multi-pass ECAP specimens at 375 °C allowed us to achieve an extraordinary strength, the highest among all the investigated cases, while the best trade-off between yield strength and elongation to failure was reached using multi-pass ECAP followed by rolling at 500 °C. This study shows a great potential of using combined deformation techniques to enhance the mechanical performance of TWIP steels.

The Domain of Portevin-Le Chatelier Effect in Al-3Mg Alloy

An Al-3Mg (wt. %) alloy was studied after equal channel angular pressing and subsequent cold rolling. The mechanical behavior of the alloy in the temperature range from 223 K to 373 K (from –50°C to 125°C) at strain rates 2.1×10–1 – 5.2×10–5 s–1 was investigated. The analysis of stress-strain curves was performed to determine the conditions of manifestation of the Portevin – Le Chatelier (PLC) effect in investigated alloy. The deformation curve at a temperature of 298 K (25°C) and a strain rate of 1×10–3 s–1 is characterized by instability of plastic flow in contrast to the deformation curves obtained under other studied strain rate/temperature conditions. Stress oscillations at the necking stage were observed at high temperatures (&gt;323 K (50°C)) and lower strain rates (1×10–4 s–1 and 5.2×10–5 s–1) forming the left border of the PLC effect domain. In general, deformation curves are characterized by the absence of stress serrations during the uniform elongation.

Effects of ECAR process on the mechanical properties of explosively welded Al/Cu/Al

ABSTRACT Equal channel angular rolling (ECAR) is a severe plastic deformation method that coated plastic deformation of sheets. This research aims to analyse the effects of equal channel angular rolling feeding routes and the number of passes on the mechanical properties of explosive-welded Al/Cu/Al multilayer sheets. Based on this study, three layers of metal sheets (Al/Cu/Al) were prepared through the explosive welding process to achieve the goals. This multilayer material been passed through the ECAR process, to investigate the number of passes affections and two different feeding routes (A and C) on the mechanical properties of the explosive welded samples. To examine changes in hardness and strength of ECAR samples, micro-hardness tests and uniaxial tensile tests were adopted. The results demonstrate that tensile strengths and microhardness increase for both routes by the ECAR process; however, it decreases the ductility. The yield strength of three layers of sheets has been increased from 92 MPa to 118 MPa and 126 MPa at the routes A and C, respectively. The results show that the toughness of the route A is greater than route C.

Effect of Final Rolling Temperature on Microstructures and Mechanical Properties of AZ31 Alloy Sheets Prepared by Equal Channel Angular Rolling and Continuous Bending.

The effects of final rolling temperature on the microstructures, texture and mechanical properties of AZ31 Mg alloy sheets prepared by equal channel angular rolling and continuous bending (ECAR-CB) were investigated. Extension twins {10–12} could be observed in the ECAR-CB deformed sheets. The increase in the number of {10–12} extension twins with increasing final rolling temperature might be attributed to the larger grain size and faster grain boundary migration. For all the ECAR-CB sheets at different final rolling temperatures, the deformation texture contains a basal texture component and a prismatic texture component, whereas the annealing recrystallization texture becomes a non-basal (pyramidal) texture with double peaks tilting away from normal direction (ND) to rolling direction (RD). With increasing final rolling temperature, the tilted angle of double peaks of annealing recrystallization non-basal texture increases. In addition, the plasticity and formability of ECAR-CB-A (ECAR-CB and then annealing) AZ31 Mg alloy sheets at room temperature can be improved by increasing the final rolling temperature.

Microstructure evolution of AZ91 alloy processed by a combination method of equal channel angular pressing and rolling

Abstract In the present work, AZ91 alloy was successfully processed by equal channel angular pressing (ECAP) for up to 16 passes and rolling (R) for multiple passes with a total reduction of 75% in addition to a combination method with ECAP plus rolling (ECAP+R). The effects of various processes (ECAP, R and ECAP+R) on microstructure evolution were analyzed and the influence of ECAP process on the rolling performance was examined. The result shows that ECAP contributed to a homogenous grain structure and formed a texture with higher Schmidt factors that was easy for rolling. A plate with smoother surface and reduced edge cracks was observed in the ECAP+R process than in the single R process. Although the microstructure of the alloy was similar after ECAP+R and R process, the sample of ECAP+R was more refined and had stronger second phase precipitation than the sample of R, which resulted in better rolling characteristics, along with the external surfaces.

The effect of temperature on the mechanical properties and forming limit diagram of Al 5083 produced by equal channel angular rolling

The primary purpose of this research is investigating the effect of increasing temperature on mechanical properties and formability of Al 5083 produced by equal channel angular rolling (ECAR) process. The present work also aims to study the feasibility of increasing temperature as an approach for solving the ductility problem of ultrafine-grained Al 5083, although some strength of the material might be sacrificed. So, the quantitative and qualitative analysis of the effect of temperature increase on mechanical properties and formability has been done. In this paper, the ECAR process has been performed at three different temperatures (i.e., 25 °C, 200 °C, and 300 °C(. Then, the investigation of mechanical properties such as yield strength, ultimate tensile strength, and microhardness after each pass of the ECAR at different temperatures has been performed. The results showed that by applying the ECAR process at a specified temperature, the mechanical and microhardness properties of the samples improved, while elongation to fracture reduced. At ambient temperature, and after the 3rd pass of the ECAR process, yield strength, ultimate tensile strength, and microhardness compared with the annealed sample increased by 94%, 19%, and 52%, respectively. Also, the mechanical properties of samples after the ECAR process in a specified pass at different temperatures have been evaluated. The obtained results showed that by increasing temperature, the yield strength, ultimate tensile strength, and microhardness of the samples decreased, but the elongation to fracture as well as the forming limit diagram (FLD) improved. The results illustrated that by applying the ECAR process at a specified temperature, the level of the FLDs moved downward. Also, the FLDs after the 3rd pass of the ECAR at different temperature have been compared. The results showed that the FLD0 (the major forming limit strain in-plane strain mode) at a temperature of 200 °C and 300 °C compared with the ambient temperature increased by 5% and 20%, respectively.

Effect of texture types on microstructure evolution and mechanical properties of AZ31 magnesium alloy undergoing uniaxial tension deformation at room temperature

Influence of texture type on mechanical properties and the evolution of microstructure and texture is thoroughly investigated via uniaxial tension experiment along rolling direction (RD) at room temperature on two different AZ31 alloy sheets. Electron backscattered diffraction (EBSD) measurements on deformed samples confirm that dislocation slip is the main deformation mechanism in as-received sheet with a typical basal texture, while dislocation slip and extension twinning (ET) both contribute to sustaining plastic strain in the sheet with a rare RD-split bimodal texture, which is fabricated by equal channel angular rolling and continuous bending process with subsequent annealing (ECAR-CB-A). Therefore, these two sheets demonstrate obviously different texture evolution during plastic deformation. As-received sheet maintains basal texture and further experience the concentration of basal poles towards normal direction (ND). However, ECAR-CB-A sheet not only undergoes the gradual diffusion and rotation of tilted basal poles to ND but also the development of a new TD-component texture. The activation of ET variants in ECAR-CB-A sheet is confirmed to play an important role in texture evolution, and the number of activated ET variants is increasing with the increase of angle between ND and c-axis. In addition, acquired mechanics data demonstrate that ECAR-CB-A sheet possesses higher fracture elongation (24%) and lower yield stress (73 MPa) as compared to as-received sample. This issue can be ascribed to the participation of ET to coordinate plastic deformation along c-axis and the easier activation of basal <a> slip in ECAR-CB-A sheet.